The attractive interaction between   $ J/\psi $   and   $ J/\psi $   has to be strong enough if X(6900) is of the molecule type. We argue that since   $ J/\psi $   decays predominantly into a   $ J/\psi $   pair, the interactions between   $ J/\psi $   and   $ J/\psi $   may be significantly enhanced owing to the three point   $ J/\psi $   loop diagram. The enhancement originates from the anomalous threshold located at   $ J/\psi $   GeV  $ J/\psi $  , whose effect propagates into the s-channel partial wave amplitude in the vicinity of   $ J/\psi $   GeV. This effect may be helpful in the formation of the   $ J/\psi $   peak.